Such a system is known from the European patent application EP-A-278 125.
In this patent application a flexible container is described having a sealing valve of relatively flexible material, such as for instance silicone rubber, polyvinyl chloride, urethane, ethylene vinyl acetate or a styre butadiene copolymer. Upon placing the container in an upside-down position and upon application of a squeezing force on the container, the sealing valve opens due to the increased pressure and a dispensing of the liquid through the slit occurs. Upon removal of the squeezing force, the slit closes and the liquid is prevented from flowing out of the container. The stiffness of the sealing valve is sufficient to prevent the slit from opening under the hydrostatic pressure of the liquid when the container is placed in an inverted position. To prevent opening of the slit during storage or transportation of the container, due to unintentionally applied squeezing forces or shocks due to falling, the sealing valve is covered by a cap having valve restraining means which prevent the concave top portion of the sealing valve from inverting. The valve restraining means comprises a first annular rim at the inside of the cap, which annular rim is adjacent to the concave top portion, and a second annular rim which is concentric with the first annular rim, which rests on the flexible sidewall portion of the sealing valve and which exerts a radially directed compressive force on the sealing valve keeping the slit closed. To allow passage of air that, upon unintentional compression of the container, is trapped inside the annular rims of the valve restraining means, to the ambient, the rims are provided with venting slots. Hereby dislodging of the valve restraining means is prevented upon sudden and unintentional compression of the container.
It is an object of the invention to provide for a system comprising a container and a liquid contained therein, the container allowing for accurate dispensing and for sealingly storing of its contents.
It is another object of the invention to provide for a system comprising a container and a liquid contained therein, in which the container has means for reducing the pressure inside the container under various storing and transportation conditions.
It is again another object of the invention to provide for a container that can be of a non-cylindrical shape.
A system according to the invention is characterized in that in the storage mode, the liquid contained in the container can build up a predetermined gas or vapour pressure, the container being in the storage mode in an upright position so that vapour in the container can contact the sealing valve, the valve restraining means allowing opening of the top portion's slit when the force exerted by the gas or vapour on the sealing valve exceeds a vapour threshold pressure.
Especially for products that build up a vapour pressure, or products that release a gas due to decomposition, such as for instance household bleaches or products containing peroxides, hypochlorides or perborates, the properties of the sealing valve can be used, not only for accurate and dripless dispensing, but also for venting of the gas or vapour to the ambient. During storage, the gas or vapour pressure can rise to between 30 and 150 mbar over the ambient pressure. Especially for flexible containers of non-cylindrical shape, this will give rise to serious bulging if no venting takes place.
By adjusting the length of the slit, the flexibility of the concave top portion of the sealing valve and the distance of the valve restraining means from the concave top portion, the vapour threshold pressure at which the slit slightly opens for venting, can be set to a desired value. So can for instance the flexibility of the sealing valve and the length of the slit be selected to give a good dispensing for a liquid having a predetermined viscosity, the vapour threshold pressure at which venting occurs during storage, being adjustable through variation of the valve restraining means. Contrary to the container that is disclosed in the European patent application EP-A-278125, it is essential for the container in the system according to the invention, to be in its upright position during storage. Hereby the sealing valve is located in the higher part of the container and the vapour will be in contact with the interior face of the sealing valve's concave top portion, thus allowing venting.
An embodiment of the system according to the invention is characterized in that the valve restraining means are formed by a protrusion extending from an interior face of the top wall towards the concave top portion of the sealing valve for adjustment of the vapour threshold pressure.
By selectively restricting the movement of a part of the concave top portion of the sealing valve upon closure of the cap, the vapour threshold pressure at which opening of the slit occurs can be lowered. In the dispensing mode, the cap is removed from the sealing valve so that the slit will open at the dispensing threshold pressure, which is to a large extent independent of the vapour threshold pressure.
In an embodiment of a system according to the invention, the protrusion comprises an interior wall, a projection of which on the concave top portion encircles the slit, the interior wall comprising a lower edge which is located above the top portion so that upon a rise of pressure in the container the interior wall and the concave top portion enclose a venting chamber. Upon increase of the pressure inside the container, the valve's concave top portion is pressed against the lower edge of the interior wall. The slit is confined within the venting chamber that is enclosed by the interior wall and the concave top portion. When the pressure in the bottle reaches the vapour threshold pressure, the slit will open and an amount of vapour is transferred into the venting chamber. Due to the resulting pressure equalisation in the container and the venting chamber, the slit closes and the concave top portion will retract so that the air entrapped in the venting chamber can vent to the ambient. By varying the diameter of the venting chamber and the distance between the lower edge of the interior wall and the concave top portion, the vapour threshold pressure can be adjusted. If desired, it is possible to adjust the vapour threshold pressure to a value which is higher than the dispensing threshold pressure by giving the venting chamber a sufficiently small diameter and placing the lower edge of the interior wall close to the concave top portion of the sealing valve.
In an embodiment of a system according to the invention, the cap has a spacing member connected to the interior face of the top wall which spacing member, in the closed position of the cap, rests on a blocking surface for restriction of movement of the valve restraining means towards the concave top portion. Hereby the position of the cap is always accurately defined with respect to the sealing valve and it is prevented that the slit is opened by pressing the cap down too far over the sealing valve.
Some embodiments of a system according to the invention will be discussed in detail with reference to the accompanying drawings.